Changes in mercury levels in harbor porpoises from the Bay of Fundy, Canada, and adjacent waters during 1969-1977

The results of mercury analyses of axial muscle, liver, kidney, brain, and other organs from 146 harbour porpoises, are presented. The object of the work was to study total levels of mercury in major organs, the fraction of it which was methylated and the variation of mercury levels with respect to body organ, sex, age, body weight and size, geographical location and time of year, during the period 1969-77. The methylated fraction was 76-100 per cent in muscle, 42 per cent in kidney and 173 per cent in liver. Differences in mercury levels in different sexes were difficult to establish but the levels rose with age in all organs and both sexes. Some slight correlation of mercury level with body weight was found and there was no evidence of a change in mercury level with time of year. Liver mercury levels decreased from 1970 to 1971, then increased again in 1974 and continued to rise. This is attributed to the dominance of mercury poor Gulf Stream water in 1971-1973, as opposed to the normal dominance by waters of the Nova Scotia current.